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# Pascal's Triangle II

## Description

Given a non-negative index *k* where *k* ≤ 33, return the *k*th index row of the Pascal's triangle.

Note that the row index starts from 0.

![](https://upload.wikimedia.org/wikipedia/commons/0/0d/PascalTriangleAnimated2.gif)\
In Pascal's triangle, each number is the sum of the two numbers directly above it.

**Example:**

```
Input: 3
Output: [1,3,3,1]
```

**Follow up:**

Could you optimize your algorithm to use only *O*(*k*) extra space?

## Solution

```cpp
class Solution {
public:
    vector<int> getRow(int rowIndex) {
        vector<int> row(rowIndex + 1);
        row[0] = 1;
        int prev, sum;
        for(int i = 1; i <= rowIndex; ++i){
            prev = 1;
            for(int j = 1; j < i; ++j){
                sum = prev + row[j];
                prev = row[j];
                row[j] = sum;
            }
            row[i] = 1;
        }
        return row;
    }
};
```